High-resolution spectral estimation: Rethinking the Fourier transform

2005 ◽  
Author(s):  
L. Griffiths
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Spectral Estimation ◽  
The Fourier Transform

The Pseudo-Atom Approximation in Direct Phase Determination of Protein Structures.

1997 ◽  
Vol 3 (S2) ◽  
pp. 1025-1026
Author(s):  
Douglas L. Dorset
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Protein Structures ◽  
Direct Methods ◽  
Direct Solution ◽  
Phase Problem ◽  
Electron Crystallography ◽  
Phase Determination ◽  
The Fourier Transform

In principle, the availability of high-resolution micrographs in electron crystallography is a direct solution of the phase problem that has been used to great advantage for the study of proteins. However, as the resolution of the determination increases, the Fourier transform of the micrograph becomes a less accurate phase source. Hence, alternative direct methods for phase determination have been evaluated, if only to extend the resolution of most reliable lower resolution phases to the limit of the electron diffraction pattern. The first demonstration of its feasibility was published in a study of bacteriorhodopsin extending 15 Å image phases to beyond 3 Å by maximum entropy and likelihood procedures i. Later studies demonstrated that convolutional methods also can be effective.In protein crystallography, there is always an interest in carrying out a true ab initio determinations, if only because of the challenge to traditional direct methods that become statistically less reliable as the number of atoms in the unit cell increases.

The absorption spectrum of C2H2 around ν1 + ν3: energy standards in the 1.5 μm region and vibrational clustering

1994 ◽  
Vol 72 (11-12) ◽  
pp. 1241-1250 ◽  
Author(s):  
Q. Kou ◽  
G. Guelachvili ◽  
M. Abbouti Temsamani ◽  
M. Herman
Keyword(s):  
Absorption Spectrum ◽  
Fourier Transform ◽  
High Resolution ◽  
Rotational Analysis ◽  
Vibrational Assignment ◽  
Calibration Standards ◽  
Vibrational Levels ◽  
Vibrational Transitions ◽  
The Fourier Transform ◽  
Anharmonic Couplings

We have recorded the Fourier transform absorption spectrum of acetylene, C2H2, at high resolution, around 6500 cm−1. The positions of the strongest rovibrational lines are measured with respect to the rovibrational lines in 3-0 of CO. They provide secondary calibration standards in that range with an accuracy of 3 × 10−4 cm−1. The rotational analysis of the data gives evidence of five vibrational levels of [Formula: see text] symmetry, in addition to the bright combination level (1010000). This is demonstrated to strictly fit the predicted anharmonic resonance pattern in that region, which permits the vibrational assignment of those extra transitions. Study of the relative intensities of the reported vibrational transitions suggests the need to include new quartic anharmonic couplings. This is supported by the rovibrational analysis of the cold bands around 8500 cm−1, involving the (1110000) bright level, which is also presented.

Fourier crystal diffractometry based on refractive optics

2013 ◽  
Vol 46 (5) ◽  
pp. 1475-1480 ◽  
Author(s):  
Petr Ershov ◽  
Sergey Kuznetsov ◽  
Irina Snigireva ◽  
Vyacheslav Yunkin ◽  
Alexander Goikhman ◽  
...  
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Intensity Distribution ◽  
Focal Plane ◽  
Bragg Reflection ◽  
Si Substrate ◽  
X Ray ◽  
Spatial Intensity Distribution ◽  
Reflection Geometry ◽  
The Fourier Transform

X-ray refractive lenses are proposed as a Fourier transformer for high-resolution X-ray crystal diffraction. By employing refractive lenses the wave transmitted through the object converts into a spatial intensity distribution at its back focal plane according to the Fourier-transform relations. A theoretical consideration of the Fourier-transform technique is presented. Two types of samples were studied in Bragg reflection geometry: a grating made of strips of a thin SiO2film on an Si substrate and a grating made by profiling an Si crystal. Fourier patterns recorded at different angles along the rocking curves of the Si 111 Bragg reflection were analysed.

scholarly journals Be Binary Systems with a Cool Companion: Are they Interacting?

1987 ◽  
Vol 92 ◽  
pp. 448-450 ◽  
Author(s):  
M. Floquet ◽  
A.M. Hubert ◽  
J.P. Maillard ◽  
J. Chauville
Keyword(s):  
Fourier Transform ◽  
High Resolution ◽  
Binary Systems ◽  
Fourier Transform Spectrometer ◽  
The Fourier Transform

AbstractHigh resolution spectrograms of the two well known Be binary systems ζ Tau and KX And were obtained , in the IR ( 2-2.5µ ), with the Fourier Transform Spectrometer of the CFHT. They do not reveal evidence of a cool giant companion.

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